Tuning Electrochemical Performance by Microstructural Optimization of the Nanocrystalline Functional Oxygen Electrode Layer for Solid Oxide Cells

Abstract

Further development of solid oxide fuel cell (SOFC) oxygen electrodes can be achieved through improvements in oxygen electrode design by microstructure miniaturization alongside nanomaterial implementation. In this work, improved electrochemical performance of an La0.6Sr0.4Co0.2Fe0.8O3‑d (LSCF) cathode was achieved by the controlled modification of the La0.6Sr0.4CoO3‑d (LSC) nanocrystalline interlayer introduced between a porous oxygen electrode and dense electrolyte. The evaluation was carried out for various LSC layer thicknesses, annealing temperatures, oxygen partial pressures, and temperatures as well as subjected to long-term stability tests and evaluated in typical operating conditions in an intermediate temperature SOFC. Electrochemical impedance spectroscopy and a distribution of relaxation times analysis were performed to reveal the rate-limiting electrochemical processes that limit the overall electrode performance. The main processes with an impact on the electrode performance were the adsorption of gaseous oxygen O2, dissociation of O2, and charge transfer-diffusion (O2–). The introduction of a nanoporous and nanocrystalline interlayer with extended electrochemically active surface area accelerates the oxygen surface exchange kinetics and oxygen ion diffusions, reducing polarization resistances. The polarization resistance of the reference LSCF was lowered by one order of magnitude from 0.77 to 0.076 Ω·cm2 at 600 °C by the deposition of a 400 nm LSC interlayer at the interface. The developed electrode tested in the anode-supported fuel cell configuration showed a higher cell performance by 20% compared to the cell with the reference electrode. The maximum power density at 700 °C reaches 675 and 820 mW·cm–2 for the reference cell and the cell with the LSC interlayer, respectively. Aging tests at 700 °C under a high load of 1 A·cm2 were performed.

An active and durable air electrode with self-generated nanoparticles decorated on the surface for reversible oxygen-ionic ceramic electrochemical cells

“…, ∼23 × 10 −6 K −1 ). 18,19 This is not compatible with the TEC values of electrolyte materials, such as yttria-stabilized zirconia (YSZ, i.e. , ∼10.5 × 10 −6 K −1 ) or gadolinium-doped ceria (GDC, i.e.…”

“…17 However, there are still some problems with these materials, e.g., La 0.6 Sr 0.4 CoO 3 (LSC) which is reported to have a high thermal expansion coefficient (TEC) (i.e., ∼23 × 10 −6 K −1 ). 18,19 This is not compatible with the TEC values of electrolyte materials, such as yttria-stabilized zirconia (YSZ, i.e., ∼10.5 × 10 −6 K −1 ) or gadolinium-doped ceria (GDC, i.e., ∼23 × 10 −6 K −1 ). 20 The large difference in TEC values can adversely affect the thermal stress and lattice strain between the electrode and electrolyte, resulting in poor interfacial bonding and potentially causing delamination during thermal cycling.…”

Nanotechnologies in ceramic electrochemical cells

“…In another report, Kamecki et al used the spray pyrolysis technique to prepare a La 0.6 Sr 0.4 CoO 3− δ (LSC) interlayer on a GDC20 electrolyte for further modification of the La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3− δ (LSCF) electrode. 345 The introduction of a nano-sized porous interlayer was found to be effective for acceleration of k chem kinetics and oxygen ion transport, reducing the total R p of the cell. A similar phenomenon could be found while depositing nano-structured LSCF on a dense GDC10 interlayer in a YSZ electrolyte-based fuel cell.…”

Unlocking the Potential of A-Site Ca-Doped LaCo0.2Fe0.8O3−δ: A Redox-Stable Cathode Material Enabling High Current Density in Direct CO2 Electrolysis

“…1 8 − 2 0 Among them, La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ has demonstrated excellent catalytic activity for oxygen evolution/oxygen reduction reaction and outstanding performance as an air electrode material for SOCs. 15 Furthermore, the presence of transition metals Co and Fe at the B-site of the perovskite structure enables their facile participation under reducing atmospheres, resulting in the formation of alloy nanoparticles embedded on the perovskite backbone, creating numerous nanoparticle/backbone interfaces. These interfaces serve as highly active sites for the CO 2 reduction reaction, thereby substantially enhancing the catalytic activity of the CO 2 electrode.…”

“…In the past few years, there has been growing interest in B-site Co-Fe-based perovskite materials as potential electrodes for solid oxide cells (SOCs) or oxygen permeation membranes due to their excellent electronic and oxygen ion conductivity, as well as their good electrocatalytic activity. − In particular, La 1– x A x Co 0.2 Fe 0.8 O 3−δ (where A = Sr/Ba/Ca and x = 0.2, 0.4, 0.6) has shown great promise as an oxygen-permeable material at intermediate temperatures. − Among them, La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ has demonstrated excellent catalytic activity for oxygen evolution/oxygen reduction reaction and outstanding performance as an air electrode material for SOCs . Furthermore, the presence of transition metals Co and Fe at the B-site of the perovskite structure enables their facile participation under reducing atmospheres, resulting in the formation of alloy nanoparticles embedded on the perovskite backbone, creating numerous nanoparticle/backbone interfaces.…”